JP3482856B2 - Liquid crystal display device and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device, and more particularly, to a structure of a TFT active matrix suitable for forming on a light weight substrate having poor heat resistance such as a plastic substrate or a polymer film. And a manufacturing method.

[0002]

2. Description of the Related Art As a thin, low power consumption display device for image information and character information, an active matrix type liquid crystal display using a thin film transistor (hereinafter referred to as TFT) is widely used mainly in a portable personal computer. is there. In this type of liquid crystal display device, along with cost reduction, weight reduction of the display module is an important issue. Therefore, in order to reduce the weight of the glass substrate, which occupies most of the weight of the module, the plate thickness has been reduced. However, there is a limit to the weight reduction due to the thin plate from the viewpoint of securing the module strength, and new measures are required. Against this background, in recent years, a technique for forming a TFT on a lightweight plastic substrate such as polycarbonate has been developed. An example of such technology is the Conference Record of the 17th International Display Research Conference (Confere
nce Record of the 17th International Display Resea
rchConference) 1997, pages M-36 to M-39.
Page.

[0003]

The greatest problem in such a conventional technique is that a high-performance TFT at a low temperature that does not damage the substrate due to the low heat resistance of the substrate.
To form. In order to solve this problem, for example, it has been attempted to form a Si film or a gate insulating film forming a TFT at a low temperature by a sputtering rig or to recrystallize the Si film at a low temperature using a pulse laser. However, the characteristics of the TFT obtained by such a low temperature process are not practically sufficient. Particularly, low-temperature formation of a high-quality gate insulating film is a difficult problem to solve. Further, the plastic substrate has not only heat resistance but also chemical resistance, and it is necessary to consider resistance to various chemicals used in the photolithography process and etching process.

As described above, there are many technical problems to be solved in order to directly form a high-performance TFT on a plastic substrate, and it cannot be easily achieved by extending the conventional process technology.

[0005]

In order to solve the above problems, the present invention takes the following measures.

In a method of manufacturing a liquid crystal display device having a pair of substrates, at least one of which is transparent, and a liquid crystal layer sandwiched between the substrates, a plurality of scanning wirings are provided on a first substrate made of glass or Si. A plurality of signal wirings intersecting with each other, a plurality of semiconductor elements arranged in a matrix in the vicinity of the intersection of the scanning wirings and the signal wirings, and an active matrix element including pixel electrodes connected to the plurality of semiconductor elements is formed. After bonding a second substrate made of a desired material such as a plastic or polymer film on the active matrix element, the first substrate is removed by means such as chemical polishing, and the second substrate is opposed to the second substrate. Thus, the manufacturing process of forming the third substrate and forming the liquid crystal layer sandwiched between them is adopted.

According to the above method, the active matrix element including the TFT can be formed on the glass substrate or the Si substrate having excellent heat resistance by the same manufacturing process as the conventional one without directly forming on the plastic substrate. It is possible to form a TFT having excellent characteristics similar to the conventional one. Further, by bonding the TFT active matrix element to a desired plastic substrate and removing the first glass substrate or the like using the plastic substrate as a base, the active matrix element can be transferred onto the plastic substrate without undergoing a high temperature heat treatment step. Therefore, a high-performance active matrix substrate can be manufactured on a lightweight substrate.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1 to 5 are sectional views showing respective steps of a liquid crystal display device showing a manufacturing method according to a first embodiment of the present invention.

A pixel electrode 130 made of ITO is formed on the glass substrate 1, and a first insulating film 25 made of SiO ₂ is formed thereon. Next, the semiconductor layer 3 is formed on the first insulating film.
0, gate insulating film 20, scanning wiring 10, interlayer insulating film 2
2, the signal line 11, the source electrode 12, and the protective insulating film 23 are sequentially formed to form a TFT active matrix element (FIG. 1).

The manufacturing method of the TFT active matrix device itself may be a method according to a normal semiconductor process. For example, the semiconductor layer 30 is formed by a method of converting an amorphous silicon film into a polycrystalline silicon film by irradiating an excimer laser after forming an amorphous silicon film at a formation temperature of 450 ° C. In addition, the first insulating film 25, the gate insulating film 20,
The interlayer insulating film 22 and the protective insulating film 23 are plasma C, respectively.
It was formed by the VD method. The formation temperature is 350 ° C. Further, the scanning wiring 10, the signal wiring 11, the source electrode 12, and the pixel electrode 130 are formed by the sputtering method.
The patterning of each film was performed by a normal photolithography method.

Next, an epoxy resin 29 is applied as an adhesive layer on the completed TFT active matrix substrate, and further a plastic substrate 100 made of polyester is bonded (FIG. 2).

Next, the glass substrate 1 is polished and removed by the chemical mechanical polishing method using the plastic substrate as a base (FIG. 3).

At this time, the I formed first on the glass substrate 1
Since the pixel electrode 130 made of TO functions as an etching stopper, it is possible to prevent the TFT element from being damaged by cutting the substrate too much. Through the above steps, a TFT active matrix device formed on a plastic substrate is obtained.

Next, an alignment film ORI2 for aligning liquid crystal molecules is applied to the polished surface, and after rubbing, rubbing treatment is performed (FIG. 4).

Finally, a light-shielding film 512, a color filter film 507, and a counter electrode 510 made of ITO are formed on one surface.
Then, the counter substrate 508 made of plastic on which the alignment film ORI1 subjected to the alignment treatment is formed and the TFT substrate previously formed are arranged to face each other with a space of 4 microns using a spacer beer or the like, and the liquid crystal composition 506 is provided between them. A liquid crystal cell using a sealed plastic substrate is completed (FIG. 5).

After that, an external drive circuit for driving the TFT is mounted to complete the liquid crystal display device.

According to this embodiment, as described above,
Since the first substrate is glass, the manufacturing method of the TFT active matrix device itself can use a method conforming to a normal semiconductor process, so that a high-performance TFT can be obtained. Due to the excellent performance of the TFT, a high definition image can be easily displayed.

In the above embodiment, the external drive circuit is TF.
I have described an example of connecting to the outside of the T substrate, but a high-performance TFT
It is also easy to form a drive circuit with a TFT by utilizing the above, and to form it on the same plastic substrate. By doing so, the number of parts related to mounting can be reduced and the cost can be reduced.

Further, since a substrate of a different type from that for forming the TFT is bonded later, various materials can be used for the substrate. By using a plastic substrate as in this embodiment, an extremely lightweight display can be obtained. The device can be realized. Although polyester is used as the substrate in the above embodiments, the substrate is not limited to this, and a plastic film such as a polycarbonate or acrylic substrate or PET can also be used. In particular, by using a plastic film for the substrate, a bendable display device can be obtained. Such an example is shown below.

(Embodiment 2) FIGS. 6 to 10 are sectional views showing respective steps of a liquid crystal display device showing a manufacturing method according to a second embodiment of the present invention.

Similar to the first embodiment, a reflective pixel electrode 131 made of Al is formed on the glass substrate 1, and a first insulating film 25 made of SiO ₂ is formed thereon.
Next, the semiconductor layer 30 and the gate insulating film 2 are formed on the first insulating film.
0, the scanning wiring 10, the interlayer insulating film 22, the signal wiring 11, the source electrode 12, and the protective insulating film 23 are sequentially formed to form a TFT active matrix element (FIG. 6).

Next, an epoxy resin 29 is applied as an adhesive layer on the completed TFT active matrix substrate, and further a plastic film 101 made of PET is bonded (FIG. 7).

Next, the glass substrate 1 is polished and removed by the chemical mechanical polishing method using the plastic substrate as a base (FIG. 8).

Next, polymer dispersed liquid crystal (PDLC) 550 is applied to the surface of the glass substrate which has been polished and removed (FIG. 9).

Finally, a counter substrate 518 made of PET having a counter electrode 510 formed on one surface is provided with a polymer dispersed liquid crystal 55.
Then, the liquid crystal cell of the reflection type on the PET substrate is completed by adhering on the surface of the substrate (FIG. 10).

In the present embodiment, since the PET film is used for the substrate and the sheet-shaped polymer dispersed liquid crystal is used for the liquid crystal layer, an extremely lightweight and bendable display device can be realized.

Further, as in the first embodiment, since the first substrate is glass, the manufacturing method of the TFT active matrix element itself can be a method in conformity with a normal semiconductor process, and therefore has high performance. It is possible to obtain various TFTs. Due to the excellent performance of the TFT, a high definition image can be easily displayed.

In the above embodiment, the external drive circuit is TF.
I have described an example of connecting to the outside of the T substrate, but a high-performance TFT
It is also easy to form a drive circuit with a TFT by utilizing the above, and to form it on the same plastic substrate. By doing so, the number of parts related to mounting can be reduced and the cost can be reduced.

(Embodiment 3) FIGS. 11 to 17 are sectional views in each step of a liquid crystal display device showing a manufacturing method according to a third embodiment of the present invention.

Similar to the first embodiment, the external connection terminal 132 made of ITO is formed on the glass substrate 1, and the first insulating film 25 made of SiO ₂ is formed thereon. Next, on the first insulating film, the semiconductor layer 30, the gate insulating film 20,
Scanning line 10, interlayer insulating film 22, signal line 11, source electrode, protective insulating film 23, reflective pixel electrode 1 made of Al
31 are sequentially formed to form a TFT active matrix element (FIG. 11).

Next, polymer dispersed liquid crystal (PDLC) 550 is applied on the TFT active matrix device (see FIG. 1).
2).

Finally, a counter substrate 508 made of polyester having a counter electrode 510 formed on one surface is adhered onto the polymer dispersed liquid crystal 550 (FIG. 13).

Next, the glass substrate 1 is polished and removed by the chemical mechanical polishing method using the plastic counter substrate 508 as a base (FIG. 14).

At this time, the I formed first on the glass substrate 1
Since the external connection terminal 132 made of TO serves as an etching stopper, it is possible to prevent the TFT element from being damaged by cutting the substrate too much. Through the above steps, a TFT active matrix device formed on a plastic substrate is obtained.

Finally, the driver circuit 600 for driving the TFT active matrix is connected via the solder SLD to
External connection terminal 132 exposed on the surface opposite to the counter substrate
The liquid crystal display device is completed by bonding to (Fig. 1
5).

16 and 17 are an overall plan view and a sectional view taken along line AA 'of the completed liquid crystal display device as seen from the TFT substrate side. In the conventional liquid crystal display device, it is necessary to form a bonding pad for mounting a driver circuit on the surface of the TFT substrate, and therefore it is necessary to provide a region for this around the display area. There was a limit to reducing the area of
In the liquid crystal display device of the present embodiment, the driver circuit is a TFT
Since it can be mounted on the back surface of the substrate, as can be seen from FIG. 17, the TFT substrate and the counter substrate can have the same size,
This has the effect of reducing the frame. Therefore, it is possible to configure a terminal device that is more compact than the conventional one.

The manufacturing method and structure of the liquid crystal display device of the present invention are not limited to the above three examples.
For example, as the TFT, an inverted stagger type element using amorphous silicon can be similarly used. Further, even a MOS transistor formed on a single crystal silicon substrate can be applied by polishing and removing the silicon substrate in the step of polishing the glass substrate. Also,
Regarding the liquid crystal display mode, for example, guest-host liquid crystal, ferroelectric liquid crystal, and the like can be similarly used in addition to TN liquid crystal and polymer dispersed liquid crystal.

[0039]

As described above, according to the present invention, a high performance TFT can be formed even on a light weight substrate having poor heat resistance such as a plastic substrate or a polymer film.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a method of manufacturing a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the first embodiment of the invention.

FIG. 3 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the first embodiment of the invention.

FIG. 4 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the first embodiment of the invention.

FIG. 5 is a schematic sectional view showing the method of manufacturing the liquid crystal display device according to the first embodiment of the invention.

FIG. 6 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the second embodiment of the invention.

FIG. 7 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the second embodiment of the invention.

FIG. 8 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the second embodiment of the invention.

FIG. 9 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the second embodiment of the invention.

FIG. 10 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the second embodiment of the invention.

FIG. 11 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the third embodiment of the invention.

FIG. 12 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the third embodiment of the invention.

FIG. 13 is a schematic sectional view showing a method of manufacturing a liquid crystal display device according to a third embodiment of the present invention.

FIG. 14 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the third embodiment of the invention.

FIG. 15 is a schematic cross-sectional view showing the method of manufacturing the liquid crystal display device according to the third embodiment of the invention.

FIG. 16 is a schematic plan view of a liquid crystal display device according to a third embodiment of the invention.

FIG. 17 is a schematic sectional view of a liquid crystal display device according to a third embodiment of the invention.

[Explanation of symbols]

1 ... Glass substrate, 10 ... Scan wiring, 11 ... Signal wiring, 1
2 ... Source electrode, 15 ... Connection electrode, 20 ... Gate insulating film, 22 ... Interlayer insulating film, 23 ... Protective insulating film, 25 ... First
Insulating film, 29 ... Epoxy resin, 30 ... Semiconductor layer, 10
0 ... Plastic film, 101 ... PET film,
ORI1, ORI2 ... Alignment film, 130, 131 ... Pixel electrode, 505 ... Polarizing plate, 506 ... Liquid crystal composition, 507 ... Color filter film, 508, 518 ... Counter substrate, 510
... counter electrode, 512 ... light-shielding film, 550 ... polymer dispersed liquid crystal, SLD ... solder, DIS ... display area, 600 ... driver circuit.

─────────────────────────────────────────────────── --Continued from the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1368 G02F 1/1333 G02F 1/1333 500 H01L 29/786

Claims (3)

(57) [Claims] 1. A step of forming an external connection terminal on a first substrate, a step of forming an insulating film on the external connection terminal, a plurality of scanning wirings on the insulating film, and a plurality of scanning wirings. A plurality of signal wirings intersecting with each other, a plurality of semiconductor elements arranged in a matrix in the vicinity of an intersection of the scanning wirings and the signal wirings, and an active matrix element including pixel electrodes connected to the plurality of semiconductor elements is formed. A step of forming the liquid crystal layer on the active matrix element, a step of forming a counter substrate on the liquid crystal layer, and a step of removing the first substrate to expose the external connection electrode. A step of connecting a driver chip containing a drive circuit to the external connection terminal on a surface opposite to the counter substrate,
And a method for manufacturing a liquid crystal display device. 2. A step of connecting an external connection electrode terminal to a first substrate, a step of forming an insulating film on the external connection electrode, a plurality of scan wirings on the insulating film, and a plurality of scans. An active matrix element including a plurality of signal wirings intersecting the wirings, a plurality of semiconductor elements arranged in a matrix in the vicinity of an intersection of the scanning wirings and the signal wirings, and pixel electrodes connected to the plurality of semiconductor elements. A step of forming, a step of arranging a counter substrate facing the first substrate, forming a liquid crystal layer between them, a step of removing the first substrate to expose the external connection electrode, Connecting a driver chip having a built-in drive circuit to the external connection terminal on a surface opposite to the counter substrate;
And a method for manufacturing a liquid crystal display device. 3. The method according to claim 1, wherein at least one of the first substrate and the counter substrate is a material containing an organic compound as a main component or a metal foil.